cAMP has profound effects on flagellar motion and has been implicated as a key regulatory molecule in the initiation of mammalian sperm motility. The long term goals of this research project are to investigate the structure and function of the flagellar-associated type II cAMP-dependent protein kinase and its binding proteins in mammalian sperm. A major goal of this proposal is to investigate the biochemical basis for the spatial segregation of the type II cAMP-dependent protein kinase between the cytosol and the various flagellar compartments. Since compartmentalization is mediated via the regulatory subunit, RII, experiments are being conducted to explore the possibilities that (a) information encoded within the primary sequence of sperm specific RII isoforms is the primary determinant of kinase compartmentalization; (b) all RII isoforms have the ability to interact with the flagellum and is mediated by the binding of RII to specific flagellar binding proteins or (c) compartmentalization is the result of posttranslational modification of RII. To gain further insight into the molecular basis of the RII:binding protein interaction, we are investigating the structural, functional and biochemical properties of the 80 and 120 kDa fibrous sheath-associated RII-binding proteins.